The purpose of this study on human lung is to increase the sensitivity of diagnosing neoplastic transformation and to advance our ability to predict the kind of chemotherapeutic agents to which the different types of lung cancers would respond best. Neoplasms and tumor-free areas of resected lobes or surgical biopsy samples will be subjected to detailed histological examination. In aliquots of the same samples, and also in human fetal lung, we shall investigate the biochemical equipment which regulates the metabolic and proliferative potential of the different pulmonary tissues. Sets of enzymes will be identified whose amount or isozyme pattern can characterize different classes of pulmonary neoplasms and the degrees of differentiation of individual tumors. We plan to show that enzyme-pathology can introduce sensitive, objective, quantitative criteria into the cytological characterization of hyperplastic foci and the early detection of precancerous lesions.